This invention generally relates to roller bearings. More particularly, the present invention pertains to roller bearings for longitudinal motion.
Roller bearings for permitting longitudinal movement are known in the art. German Utility Model DE 81 24 026 U1 describes a torque-transmitting bearing for longitudinal motions in which at least one race plate is fixed in a radially adjustable manner in a housing bore. To avoid the need for intervention into the housing, the race plate has axially extending cutting edges. When the bearing is press-fitted in place, these cutting edges dig into the face of the bore in the housing. The race plate can thus be aligned with the race of the shaft.
A similar roller bearing is known from German Utility Model DE 81 24 025 U1. To prevent mistakes during installation, caused by production variations and imprecision, from adversely affecting the running or operating properties of the roller bearing, this document describes that when the race plates are being positioned, an annular blade disposed on the face end of the housing screw digs into a plastically deformable inlay of the race plate. This enables the race plate to align itself automatically.
With these known types of linear guides, it can thus be assured that the race plates will become solidly fixed in a desired position upon installation of the linear bearing. Certain production variations can be eliminated as a result. However, a disadvantage of the previously known versions is that this kind of bearing composite can react only slightly, if at all, to altered kinematic conditions, such as if during operating conditions the relative direction of rotation between the sleeve part and the guide rod changes constantly. Such a situation is relatively typical, for instance, in the linear bearing guide of the steering column of a motor vehicle.
A need thus exists for a roller bearing for longitudinal motions in which a flexible reaction in terms of the position of the race plates is assured even if the direction of rotation of the guide rod relative to the sleeve part changes constantly, with production variations nevertheless remaining without adverse effect within a certain scope.
A need also exists for a longitudinal motion roller bearing that addresses the foregoing while at the same time assuring that the guidance property of the linear bearing remains relatively unchanged even after long use, with material fatigue not having any significant adverse effect on the guidance precision of the bearing.
In accordance with one aspect of the invention, a roller bearing for longitudinal motion includes a sleeve part provided with a bore and a plurality of uniformly distributed receptacles formed in the inner surface of the sleeve part, a guide rod positioned in the bore in the sleeve part, a plurality of race plates each disposed in one of the receptacles in the sleeve part, a plurality of roller bodies disposed between the race plates and the guide rod, and a spring mechanism operatively associated with at least one of the race plates to provide a spring force acting on the at least one race plate.
The spring mechanism helps ensure that the roller bodies are always pressed into their assigned position with a constant force, namely the spring force associated with the spring mechanism, so that the roller bearing is relatively invulnerable to production variations that systematically can never be entirely avoided with respect to the individual components of the bearing. As a result, a relatively inexpensive production of the bearing can be achieved. Also, fatigue effects in the individual components of the bearing do not play a major role because the spring mechanism can counteract the yielding of individual elements. Further, even if the direction of rotation of the motion between the guide rod and the sleeve part reverses itself constantly or continually, relatively little or no loss of precision takes place because the spring mechanism generally always ensures constant rolling conditions.
The race plates can be sized or configured to provide play in relation to the receptacles receiving them. As a result, the spring mechanism according to the invention can come into play especially efficiently.
The spring mechanism preferably acts in the radial direction of the sleeve part. In addition or as an alternative, the spring mechanism can act in the lateral or somewhat circumferential direction of the sleeve part.
It is envisioned that the receptacles receiving the race plates can be formed in the outer surface of the guide rod rather than being formed in the inner surface of the sleeve part.
The spring property associated with the spring mechanism can be integrated directly into the race plate. For example, the spring mechanism can be embodied integrally with the respective race plate by virtue of, for example, the material forming the race plate. For this reason, the race plate can be given a special form, designed such that yielding or sagging of the race plate occurs under load, so that the plate develops a certain spring action.
The spring mechanism can also be in the form of a spring mechanism that is separate from the race plate and placed between the race plate and the sleeve part (or the guide rod when the receptacles are formed in the guide rod). To that end, it is preferable that the spring mechanism be placed in a chamber formed between the receptacle for the race plate in the sleeve part or in the guide rod and the race plate itself. The race plate can also be provided with its own recess or receptacle which forms the chamber for the spring mechanism.
As the spring mechanism, wavy or undulating metal parts, in particular spring metal strips, are quite useful. Also, the spring mechanism can be operatively associated with only one race plate, or a few race plates.
According to another aspect of the invention, a roller bearing for longitudinal motions includes a sleeve part provided with a bore, a guide rod positioned in the bore in the sleeve part and including a plurality of uniformly distributed receptacles formed in the outer surface of the guide rod, a plurality of race plates each disposed in one of the receptacles in the guide rod, a plurality of roller bodies disposed between the race plates and the sleeve part, and a spring mechanism operatively associated with at least one of the race plates to provide a spring force acting on the at least one race plate.
According to another aspect of the invention, a roller bearing for longitudinal motions includes a sleeve part provided with a bore, a guide rod positioned in the bore in the sleeve part, a plurality of uniformly distributed receptacles formed in either the outer surface of the guide rod or the inner surface of the sleeve part, a plurality of race plates each disposed in one of the receptacles, a plurality of roller bodies positioned between the guide rod and the sleeve part, and a spring element positioned between at least one of the race plates and the receptacle in which the at least one race plate is disposed to apply a spring force to the race plate urging the race plate in a radial direction away from the closed end wall of the receptacle.